| As the basic part in various machines, gear's quality affects the machines' quality directly. Gear's tooth surface quality and tooth modification have an important influence on its working performance and working life. Lots of studies have proved that gear's working performance and working life could be improved greatly by improving the tooth surface quality and modifying the tooth suitably. So, if the gear's tooth is finished and modified, its quality will be enhanced undoubtedly.Pulse Electrochemical Finishing (PECF) and Electrochemical Mechanical Finishing (ECMF) are two kinds of nontraditional finishing process, which could finish the workpiece surface with any hardness efficiently and have been used as the finishing process of various parts. So, there is a great significance to apply PECF and ECMF to finish gear's tooth surface for improving its quality. Based on the analysis of the characteristic of the existing gears' finishing process and the structure of the gear, this paper studies the application of PECF and ECMF in the finishing process of gear's tooth.The general rule of anodic finishing and removal depth distribution in PECF and ECMF are analyzed theoretically and experimentally. For anodic finishing, by studying the difference of dissolving velocity in different area of anodic micro-surface, this paper brings forward a new theory to explain the anodic smoothening, which is named normal direction dissolution. With this theory, the finishing characteristics of PECF and ECMF are analyzed in detail. For tooth modification, the removal depth distribution in PECF with a moving cathode is discussed on the basis of Faraday Rule and the removal depth distribution in ECMF is discussed on the basis of the influence of mechanical action on the electrochemical action, which provides a foundation for the tooth modification in the finishing process.Based on the above discussion and according to the structure of gear, the applications of PECF and ECMF to the gear are discussed.In the study of PECF's application to the gear surface finishing, different application schemes are compared and it is found that PECF with a tooth profile shaped cathode is a preferable scheme. The key technologies to achieve both profile and lead modification in finishing process are discussed as follows: tooth profile modification with an uneven interelectrode gap distribution, tooth lead modification with the variable moving velocity of the cathode, design of the tooth profile shaped cathode and influence of the finishing on the gear's precision. To prove above points, the experiments were carried out. The experimental results show that the tooth surface roughness Ra could be decreased from 3.9μm to 0.35μm, which means that this process possess the finishing ability for the raw surface tooth, and the tooth profile and lead could be modified.In the study of ECMF's application in the gear surface finishing, different application schemes are compared and it is found that evolving mode is a preferable scheme. The following key technology issues are studied: the spatio-temporal matching of electrochemical action and mechanical action with a modified involute profile cathode, the matching of electrochemical action and mechanical action intension, tooth lead modification by the unevenness of mechanical action distribution and influence of finishing on gear's precision. Then the experiments were carried out. The experimental results show that the tooth surface roughness Ra could be decreased from higher than 1.0μm to about 0.1μm, the tooth topography is improved obviously, the drum-like tooth is obtained and the gear's precision is improved to a certain extent. Finally, the ECMF machine for cylindrical gear is developed.The characteristics of above methods are discussed. PECF is applicable to those special gears, such as the inside meshed gear, the large gear and etc, and ECMF is applicable to those volume-produced outside meshed gears, such as the gears used in the car, motorbike and engineering machine etc.
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